Yarn relaxation process using fluid jets



Dec. 25, 1962 Filed April 2, 1959 FIG! Kane/a1- J l zer' INVENTORS BY BATTORNEY and Company, Wiirnington, Del a corporation of Delaware FiledApr. 2, 1959, Ser. No. 893,731 12 filaims. (03!. 57-157) This inventionrelates to an improved method for offecting the controlled relaxation ofyarns composed of synthetic linear polyamides, polyesters, and the like.More specifically, this invention has reference to relaxed interlacedyarns and to their production in a single, continuous operation.

US. patent application Serial No. 661,095, filed May 23, 1957, nowabandoned and Belgian Patent 567,997 to G. Pitzl, disclose a highlyuseful process which permits preparation of freshly drawn nylon yarnexhibiting reduced residual (boibofii) shrinkage achieved with asubstantial improvement in intrapackage uniformity of yarn tensileproperties. Such improved yarns are prepared by relaxing freshly drawnnylon yarn in a controlled, i.e., metered amount, then winding the yarnonto a package within a specified range of tension. Prior art relaxationor preshrinking procedures, being uncontrolled, invariably have led toyarn showing poorer uniformity of intrapackage yarn properties, relativeeven to those of the supply yarn. The improved controlled relaxationprocess is quite attractive commercially, representing the firstpractical solution to the problem of pirn taper barre, which contributesto the production of fabrics essentially free from streaks, barre, andthe like defects.

In yarn packaging processes, the windup usually is either a twister or areciprocating traverse, the latter being employed when zero-twist yarnsubsequently can be utilized. However, the number of applications forzero-twist yarn is definitely limited since such yarn performs ratherpoorly in many of the common textile operations, owing to a loosness ofstructure which increases the incidence of broken filaments. By twistingthe yarn into a compact structure, such difliculties are usuallyavoided, but only at the expense of process speed and flexibility. II"it were possible to circumvent the twisting operation while stillpackaging a compact structure free from the potential shortcomings ofordinary zero-twist yarn, the above-described process could be carriedout substantially continuously at high speeds with reduced equipment andoperator costs.

A primary object of this invention is to provide a relaxed interlacedyarn, i.e., a yarn prepared by controlled relaxation procedures andwhich, even at zero-twist, has handling characteristics at least theequal of conventional twisted yarn. Another object is to provide such ayarn composed of poly(hexamethylene adipamide). Yet another object is toprovide such a yarn which is composed of poly(ethylene terephthalate).Another object is to provide freshly drawn yarns composed ofpoly(hexamethylene adipamide) which have been continuously relaxed in acontrolled amount in excess of about 12%. A still further object of thisinvention is to provide a warp, tow, package, or fabric made up at leastin part of yarns of the foregoing types.

Another object of this invention is to provide a process whereby yarnscomposed of synthetic linear polyamides, polyesters, and the like arerelaxed in a controlled manner and simultaneously interlaced to form acompact uni tary strand, both steps being carried out in a single rapidand continuous operation. A further object is to provide such a processwhereby the yarn is freshly drawn immediately prior to simultaneousrelaxing and interlacing.

Patented Dec. 25, 11962 A still further object is a process wherebyyarns composed of poly(hexamethylene adiparnide) are relaxed in acontrolled amount in excess of about 12%. Still another object is aprocess for relaxing yarn in a continuous controlled manner, the processutilizing hot air at relatively convenient temperatures as the relaxingmedium. These and other objects, together with the means foraccomplishing them, will appear hereinafter.

The objects or" this invention are accomplished by an improved methodwhich comprises forwarding a relaxable filamentary structure composed ofsynthetic linear polyamides, polyesters, or the like at uniformlypositive tension through a zone of fluid turbulence, directing a heatedfluid into the zone onto the filamentary structure with sufiicient forceto separate the filaments of the structure and interlace them into acompact unitary strand, simultaneously permitting the filamentarystructure to relax in a controlled, i.e., metered amount, and thereafterwinding it into a package at a sufficiently reduced tension thatimmediate or subsequent elongation of the yarn is substantially avoided.A preferred embodiment, where very low shrinkage is required, e.g., forwelt yarns, comprises relaxing, with air at a temperature between about350 and about 450 (3., a freshly-drawn yarn composed ofpoly(hexamethylene adipamide) in controlled amount in excess of about12% based on the length of the filaments of the structure,simultaneously interlacing the same, and continuously thereafter windingthe yarn onto a package at a tension of from about 0.05 to about 0.15gram per denier. In another preferred embodiment, such as for weavingyarns, freshly drawn yarn is relaxed in a controlled amount from about 7to 12%, based on the length of the filaments of the structure, and isthereafter wound up at 0.05-0.35 g.p.d. tension.

There results from this process a relaxed interlaced yarn, i.e., acompact unitary strand maintaining its unity even when the bundle is atzero-twist, and which exhibits substantial reductions in residualshrinkage achieved with substantial improvement in intrapackageuniformity of yarn properties.

The yarn is composed of filamentary structures which are randomlytwisted and interentangled throughout the structure. In general, theyarn has a residual shrinkage below about 7% and contains filamentswhich are sufiiciently interentangled to provide the yarn at zero bundletwist with handling properties of a true twist yarn of the samecomposition and having at least /2 turn per inch twist.

The filaments of the yarn are composed of partially oriented,thermoplastic synthetic polymeric compositions, preferably polyamidesand polyesters, such as poly(hexamethylene adipamide) and poly(ethyleneterephthalate). Such a product is obtained in a surprisingly rapid andcontinuous manner, presumably owing to the unexpectedly high rate ofheat transfer from the relaxing medium to the yarn, which isparticularly apparent in the use of a fluid jet apparatus.

The invention is applicable to yarns, filaments, and similar strandswhether spun or continuous; continuous multifilament yarn, shortened toyarn, will be employed hereinafter as exemplary of all such strands,since in this form the invention has its greatest utility.

FIGURE 1 shows schematically an apparatus assembly useful in thepractice of the prior art.

FIGURE 2 shows schematically an improved and preferred arrangement ofapparatus for accomplishing the process of this invention.

FIGURES 3a, 3b and 4 show various fluid jets which are useful in thepractice of the present invention.

FIGURE 5 illustrates a relaxed interlaced yarn.

Referring to FIGURE 1, an undrawn yarn 1 is withdrawn from package 2,passed through pigtail guide 3,

aoeaess and then passed in multiple wraps about driven feed roll 4 andassociated separator roll 5. From feed roll 4, the undrawn yarn 1 passesin several wraps about snubbing pin 6, as taught by Babcock in US.Patent 2,289,232. The yarn is drawn in frictional contact with pin 6under the urging of draw roll 7 and its associated separator roll 8.Draw roll 7, of course, has a higher peripheral speed than feed roll 4,whereby the yarn is elongated to several times its original length. Fromdraw roll 7, the yarn passes through relaxing means, in this case oven99 with jacket 10 (heating means not shown), to relaxing and itsseparator roll 12. The relaxation permitted the yarn is controlled byadjusting the relative peripheral speeds of rolls 11 and 7. The yarnnext passes through pigtail guide 13 and is wound onto a tapered twisterp:1ck age 16 by means of ring 14 and associated traveler 15. The tensionin the yarn Wound to package 16 is controlled by the weight of traveler15, as is well known in the art.

Referring now to FIGURE 2, an undrawn yarn 1 is forwarded by suitableadvancing means (not shown, see FIG. 1) to a non-rotating snubbing pin17 (Babcock U.S. 2,289,232), makes one or more wraps thereabout, beingdrawn in frictional contact therewith under the urging of draw roll 18with its associated separator roll 19. The yarn then passes from drawroll 18, traverses fluid jet 19, changes direction over idler roll 29,and passes in multiple wraps around the relaxing roll 21 and itsassociated separator roll 22, following which the yarn is lead to awindup (not shown, see e.g. FIG. 1) and is packaged in conventionalmanner. The controlled relaxation of this invention is achieved by theperipheral speeds of the draw roll 18 and relaxing roll 21 components ofthe stepped roll 23 (similarly, portions 19 and 22 of the steppedseparator roll 24) differing in proportion to their diameters; the yarnis thereby relaxed to an extent proportional to the ratio of diametersof the drawing and relaxing rolls. Relexation is initiated by the actionof heated fluid being supplied to the yarn in fluid jet 1%, whereininterlacing of the yarn components simultaneously takes place. The feedyarn 1 may be supplied from a package or a spinning machine; the drawingand relaxing steps need not be carried out sequentially. The illustratedembodiment is a most compact and economical apparatus arrangement foraccomplishing relaxing and interlacing in accordance with thisinvention.

FIGURES 3a and 3b show a fluid jet preferred for use in the presentinvention. Fluid jet 2 has a lengthwise yarn passageway 23 which, inthis embodiment, is substantially cylindrical in form throughout itslength. Fluid conduits 24a, 24b, 24c, 24d intercept on passageway 23 atright angles to the wall thereof and are positioned so that thelongitudinal axis of each fluid conduit and yarn passageway 23 interceptperpendicularly. Fluid conduits 2 2a and 24b and 240 and 240' arearranged as opposed pairs spaced longitudinally along the yarnpassageway with their respective longitudinal axes perpendicular. Fluidjet 2 also has lengthwise slot 28 to facilitate stringing-up operations.Optionally, all of fluid jet 2 may be enclosed in a concentriccylindrical jacket, suitably tapped, to provide manifolding of theheated relaxing fluid to each of the fluid conduits.

FIGURE 4 shows another useful fluid jet which contains a lengthwisecylindrical yarn passageway 25 perpendicularly intercepted by a singlepair of opposed fluid passageways 26a and 260, the latter being suppliedby fluid ducts 26 and 2612. In addition to supplying fluid conduit 26c,fluid ducts 25 and 26b serve to create a fluid curtain in stringup slot27. The fluid curtain facilitates yarn stringup and, at the same time,prevents the yarn from blowing out of yarn passageway 25. Obviously,numerous modifications in the design of the fluid jet may be made. Manyother suitable fluid jets are shown in US. application Serial No.752,451, filed August 1, 1958, now abandoned, to W. W. Bunting and T. L.Nelson. Another roll it 4 suitable fluid jet is shown in FIGURE 10 ofU8. Patent No. 2,852,906 to A. L. Breen.

In operation, the fluid jet is positioned intermediate suitable yarnforwarding means, i.e., means capable of advancing the yarn through thefluid jet at uniformly positive tension, such as the apparatus shown inFIGURES 1 and 2. The fluid jet is continuously supplied with heatedfluid under pressure, which fluid is directed into the yarn passagewaythrough the fluid conduits. The heated fluid on entering the yarnpassageway creates a zone of fluid turbulence which causes the yarnbundle to be opened, i.e., the filaments separated, and simultaneouslycauses the individual filaments to be twisted and intermingled in apurely random manner to produce a compact interlaced yarn.

Such an interlaced yarn is shown in FIGURE 5 and is a very stableconsolidated structure which performs and iandles in the same manner asa true-twist yarn. In addition to being interlaced, the individualfilaments in the yarn are rapidly and uniformly heated by the impingingfluid while the bundle is opened. The surprisingly efficient and uniformtransfer of heat to the individual filaments in the yarn bundle causesthe yarn to relax readily, in an amount depending on the relativeforwarding and advancing speeds. The unexpectedly high rate of transferof heat from the heated fluid, i.e., the relaxing medium to the yarnmakes possible controlled relaxations in amounts heretoforeunattainable, and results in yarns having great- 13/ reduced residualshrinkage achieved with excellent uniformity of properties, in additionto being interlaced. Moreover, owing to such efliciency of heattransfer, relaxing fluids at much lower temperatures than normallyemployed may be utilized.

Among the important variables which affect the process of this inventionare the pressure of the relaxing fluid and the yarn tension in therelaxing zone, which affect the density of interlacing; the temperatureof the relax-- ing fluid, and the yarn denier and speed which affect theextent of controlled relaxation. These various factors are described inconsiderable detail in the above-mentioned Bunting and Nelsonapplication and in the Pitzl application, which relate to interlacingand controlled relaxing, respectively. Insofar as product uniformity andthe effective amount of relaxation, which ultimately affects the extentof reduction of residual shrinkage, is concerned, the yarn tension atthe windup appears controlling. For this reason, it is preferred thatthe windup tension be between about 0.05 and about 0.35 gram per denier,preferably less than about 0.25 gram per denier, tending progressivelytoward the lower value as the extent of controlled relaxation isincreased. Otherwise, if the yarn tension is too high at the windup,some redrawing may occur, i.e., some of the percentwise re laxation islost due to attenuation or elongation of the yarn under the influence ofexcessive windup tension. In this connection, it has been observed thata winding tension of about 2 grams absolute represents the least tensionwhich can be used in a practical process. It is essential to maintainwinding tension high enough to prevent sloughing of the package duringshipment, but low enough to prevent objectionable redrawing of the yarn.

The density of interlacing is directly proportional to the pressure ofthe relaxing fluid, as supplied to the fluid jet. The amount ofcontrolled relaxation also depends, in part, on the pressure of therelaxing fluid, which, together with tension, determines the extent ofyarn bundle opening.

Any fluid reasonably inert to the yarn may be employed as the relaxingagent, with hot air being preferred in many applications. The fluid maybe a liquid or gas at the temperature of operation, but inert gaseous material such as steam, nitrogen, carbon dioxide, etc., are preferred. Forbest results, the interlacing fluid should reach a velocity of about /2sonic velocity or more, immediately prior to impinging upon the yarn, Athigher encased velocities, less dense fluids may be employed. For thepresent purposes, heated air at pressures between about p.s.i.g. andabout 100 p.s.i. are desirable, with pressures between about p.s.i.g.and about 30 p.s.i.g. being preferred. To achieve a desired amount ofcontrolled relaxation, the temperature of the air is inversely relatedto the pressure, i.e., the higher the temperature, the lower thepressure required. The temperature of the fluid should not be so high asto be deleterious to the yarn, e.g., cause fusion or degradation of thefilaments, nor should it be so low that insuificient relaxation results,leading to slackness in the yarn line. Of course, fluid pressurerequirements and hence fluid consumption are related to the dimensionsof the fluid jet.

For example, at a pressure of about 15 to about 30 p.s.i.g.,temperatures between about 200 and about 500 C. are suitable. Thetemperature of the fluid should not be so high as to be deleterious tothe yarn, e.g., cause fusion or degradation of the filaments, of course,fluid pressure requirements and hence fluid consumption are related tothe dimensions or" the fluid jet.

Proper control of yarn tension in the vicinity of the fluid jet also isan important factor atfecting interlacing ensity, which varies inverselywith the yarn tension. The yarn tension should be uniformly positive inthe relaxing zone, i.e., should be maintained at a constant valueexceeding that tension which derives from the weight of the yarn per se,sufficiently high to avoid looping, curling, or crimping of the yarn. itis characteristic as well as necessary in a controlled relaxation thatthe yarn line never becomes slack. To further uniformize yarn tension inthe relaxing zone, inline fluid jets, such as those shown in FIGURES 24,are preferred, since such jets offer no snubbing surfaces nor divert theyarn path. In controlled relaxations, especially in amounts in excess ofabout 12%, ths yarn tension is normally self-seeking, running at uniformvalues between 1 and 2 grams in the steady state. These values aresufliciently low to permit interlacing of quite ample density. Althoughsatisfactory interlacing can be attained at higher tensions, tensionsexceeding about 5 grams rarely occur during controlled relaxations. Theeliects of excessive tension can always be overcome by an increase inthe pressure of the relaxing fluid. Finally, the density of interlacingappears to be insensitive of yarn speed.

Although steam is an efllcacious relaxing agent, hot air is usuallypreferred for its availability and lack of condensation in its use. Hotair at temperatures in excess of about 180 C. is capable of producingcontrolled relaxations of about 12% or more in 66-nylon. Sincerelaxation apparently is accelerated by moisture, the yarn can be Wetwith water, a solution of a swelling agent (V. Miles, US. 2,157,119), orthe like prior to relaxation with hot air in the fluid jet. Optionally,the yarn may be preheated prior to encountering the fluid jet, e.g.,using an oven, such as shown in FIGURE 1. Of course, the temperature ofthe relaxing agent is limited some what by the stability characteristicsof the polymer from which the yarn has been prepared. The yarn speeddetermines the extent of relaxation at any given temperature of therelaxing medium, since at increasing speeds, the time of exposure of theyarn to the relaxing fluid is decreased. For example, at 100 yards perminute the yarn remains in a /2-inch jet for about 0.01 second; at 500yards per minute, the exposure time is reduced to less than 0.002second. Multiple fluid jets may he employed in instances Where it isdesirable to increase exposure times without decreasing yarn speeds. Thetemperature of the relaxing medium should be increased and/ or the yarnspeed decreased for higher denier yarns, in order to compensate for thegreater mass of such filaments.

The following examples illustrate specific embodiments of thisinvention.

EXAMPLE 1 Poly(hexamethylene adipamide) yarn of 34 filaments and spundenier of 208 (23 tax) is drawn to a final denier of about (7.6 tex)using the prior art apparatus substantially as shown in FTGURE 1.Immediately after drawing, the yarn is subjected to a series ofrelaxation treatments, using the same apparatus. The yarn is relaxed inrelaxing means i which in the present experiment is an oven, 12 inchesin length. The yarn speed in the oven is 562 yards per minute, hence theexposure time in the oven is about 0.03 second. The windup tensionthroughout this series of tests is maintained at 0.17 gram per denier(g.p.d.). Table I shows the improvement in yarn shrinkage and shrinkageuniformity under various conditions of relaxation.

Table 1 Percent shrinkage Percent Test relaxa- Medium and temp.

tion Avg. Range AA"- None 9.1 an-.- Stoam,100 (3.- 7.5 AC0" 8 0 do 7.2AD. 12.0 moo All..- 5 12 0 Suparheatetl ste m 43 AF. 6 12. 0 an, ans-000C.-- 4. 4

1 A erage residual shrinkage of the yarn.

Maximum difference in residual shrinkage between samples taken from thesame bobbin.

3 Uncontrolled. Inoperable.

5 x arn windup tension is 0.05 g.p.d. in these two tests.

After treating the yarn samples under the conditions shown in Table 1,packages of each sample are maintained for 7 days at F., 72% relativehumidity prior to testing. The yarn samples are obtained by strippingyarn from the package, taking representative samples of to cm. inlength.The samples are taken from the extremities of the package and from thelongitudinal center of the package, throughout the entire package.

Sample length is determined immediately after removal from the package;the ends of the yarn segment are knotted together, a weight of about 0.1g.p.d. is hung in the loop, and the length of this loop measured. Afterdetermining the initial length, the loop of yarn is submerged in boilingwater for about 20 minutes, after which it is removed and dried about 25minutes under the 0.1 g.p.d. tension. The length of the boiled-off loopis measured and the percent shrinkage is calculated based on the lengthof the original sample.

Test AA shows typical values for What amounts to a conventional drawingprocess, without provision for relaxation and without use of the heatingoven. The average residual shrinkage level of yarn processes under theseconditions is 9.1%, with an average residual shrinkage range of 1.7%through the bobbin. Under the conditions of test AA, of course, the yarnby-passes rolls 11, 12.

Test AB represents the same conditions as test AA, except that steam at100 C. is introduced into oven 9. The yarn is thus permitted to relax asmuch as possible under the established winding tension of 0.17 g.p.d.,but the amount of relaxation is not controlled by means of rolls l1, 12.Under these conditions, the average shrinkage is 7.5%, but there is aneven greater shrinkage spread (2.0%) than was the case with conventionaldrawing (test AA). This result is typical of those obtained by prior artuncontrolled relaxation procedures.

Test AC shows the advantages obtained with a controlled amount ofrelaxation, initiated in this case by the 100 C. steam in oven 9. Thereduction in residual shrinkage is comparable to that attained in testAB; however, unlike the latter test, the shrinkage range is decidedlyimproved in test AC. in test AD, the upper limit of relaxation under thepresent test conditions has been exceeded, as evidenced by thedeterioration of threadline stability to the point of inoperability,where severe backwrapping on the relaxing rolls i1 and .12 causes theyarn line to break down.

In test AE, by increasing the steam temperature, the yarn can be relaxedin a controlled amount of 12%. This figure represents about thepractical upper limit of relaxation using ovens, steam tubes, or thelike.

In test AF, no steam is admitted to oven 9; the oven is heated by meansof electrical heaters embedded in the jacket 10. The yarn is thussubjected to radiant heat from the walls of the oven. A thermocoupleplaced within the oven, prior to introduction of the yarn, registers anair temperature of SOD-600 C. This test illustrates the strikingdifference between the eficacy of steam and hot air as relaxing media inovens, hot tubes, and the like apparatus.

Fabrics woven from the yarns of tests AA and AB show a severestreakiness and [Jim taper barr. Fabric woven from the yarn of test ACis much improved in this regard, and the fabrics from the yarns of testsAE and AF are excellent.

EXAMPLE II Poly(hexamethylene adipamide) yarn of 13 filaments is drawnto a final denier of 40 (4.4 tex) using the apparatus of FIGURE 1modified by the fluid jet shown in FIGURE 3 for the prior art oven shownin the apparatus of FIGURE 1 and by the addition of the preferredstepped draw roll assembly shown in FIGURE 2. Relaxation is effected byusing the fluid jet shown in FIGURE 3, which jet is /2 inch in lengthand is interrupted /8 of an inch from each end by 2 pairs of opposed(l80) fluid conduits, the separate pairs having their commonlongitudinal axis at right angles, each With respect to the other. Thediameter of the yarn passageway i 0.052 inch; each of the fluid conduitsis 0.025 inch in diameter. The relaxing agent is supplied to each of thefluid conduits at about the same temperature and pressure. The resultsof a series of relaxations using hot air and superheated steam at 316 C.and 18 p.s.i.g. pressure are shown in Table II. The yarn speed duringthe relaxation step is 560 y.p.m., hence the time of exposure (yarn inthe jet) is less than about 0.0015 second. Tension at the windup isabout 4 grams, and is about 12 grams in the relaxing zone.

difler from prior art procedures involving preshrinkage, setting, andvarious other phenomena; in such cases residual shrinkage usually islinearly related to the amount of lengthwise retraction, reductionstherein being achieved without appreciable improvement in differentialshrinkage properties. By using higher temperatures (particularly) and/orpressures, the residual shrinkage of the yarn can be further reduced.This is shown by the parenthetical entries under Air in Table II.

All of the yarns produced in this example are interlaced. The density ofinterlacing is about same within the two series; this behavior isexpected since the yarn tension remains about the same throughout thesetests, yarn tension being a prime interlacing variable. Similar resultsare obtained in this example when the polyamide is poly(e-caproamide).

Other fluid jets also are suitable for use in the process of thiinvention, as will be exemplified. The jet of FIG- URE 10 of US.2,852,906 is used to relax the yarn of this example with 200 C. air at30 p.s.i.g. pressure to obtain th Table IIA results.

Table IIA Test Percent shr inka ge Percent relaxation EXAMPLE III Usingthe fluid jet of FIGURE 4 in the apparatus of Example II, l7-filamentyarn composed of poly(ethylene terephthalate) is drawn to a denier ofabout 35 (3.8 tex), then relaxed in a controlled amount. The fluid jetis 4 inch long, has a 0.050-inch diameter yarn passageway, and a pair ofopposed (180) 0.025-inch diameter fluid conduits. The drawing apparatuis modified so as to include heated plates rather than a draw pin incontact with the yarn in the drawing zone, in order to draw the yarn.Air presure is 70 p.s.i.g. through this series of tests. The results ofthese tests are shown in Table 111.

Table III Draw ratio Percent relaxation Hot plate Air temp, 0.

Percent Table II Percent slrinkage 3 Interlares/inch 1 Test Percentrelaxation Air 2 Steam Air Steam 1 Determined as in Example I.

2 Determined by weighted (1.5 gram) hook; the method is described in Us.application S.N. 752,451 filed Aug. 1, 1958.

3 Parenthetical values refer to runs using 360 0., 40 p.s.i.g. air.

The results in Table II show the outstanding improvements characteristicof this invention. Operability in all cases is satisfactory, with testBC considered to be the optimum balance of both yarn properties andoperability. Quite unexpectedly, hot air appears to be somewhat moreefliciacious as a relaxing medium than steam. The high levels ofcontrolled relaxation evidenced in tests BA through BE are quitesurprising considering the abbreviated exposure times, ca. 20 times lessthan those of Example I. The results seen particularly in tests BC-BEare characteristic of controlled relaxation, i.e., progres sively lessadditional reduction in residual shrinkage is attained by increasing theamount of relaxation as the upper limit of relaxation is approached.These results EXAMPLE IV The procedure of Example II is repeated inorder to examine the effects of temperature and pressure in theoperation of this invention. The results are reported in Table IV.

Table IV Pressure series 1 Temperature series 3 Test Test PercentPressure,

' shrinkage Percent Temp,

C. shrinkage 60-13 p0ly(hexan1ethylene adipamide) yarn, 16.5%relaxation, 2121 40-13 poly(hexamethylene adipamide) yarn, 16.5%relaxation, 40

p.s.1.g.

These results show that for any given amount of relaxation thepercent-wise residual shrinkage decreases as the temperature or presureof the relaxation medium is in-.

creased. The density of interlacing throughout the ternperature seriesremained substantially constant; interlacing density is seen to increasewith increasing pressure.

EXAMPLE V The apparatus asesmbly of Example IT is used to examine theeffects of varying draw ratio, yarn denier, yarn count, and yarn speedon residual shrinkage of poly(hexamethylene adipamide) yarns. The testyarns are relaxed 13.5% with 220 C. air; the air how is 0.95 s.c.f.m.The yarn speed is 790 y.p.m. (ca. 0.001 second exposure in the jet).

The results show that the drawing speed has an appreciable affect on theultimate level of residual shrinkage (compare test series EA-ED andEi-EL),- the effective amount of relaxation depends inversely on yarndenier (compare tests EA and EH), and, for the lower denier yarn, theeffective amount of relaxation depends directly on the draw ratio (testseries EA-ED and EIEL). In each series of tests, the density ofinterlacing is about the same.

EXAMPLE VI Supplementing Example IV, the apparatus assembly of thatexample is utilized to prepare at various air temperatures and pressure40 denier (4.4 tex) 13 filament yarns of poly(hexamethylene adipamide)having predetermined amounts of residual shrinkage. The results arerecorded in Table VI.

Table VI 2% residual shrinkage 1.8% residual shrinkage Run Run Temp.,Pressure Temp Pressure C. p.s.i.g. C p.s.i.g.

These data show that desired levels of residual shrinkage can beachieved at various temperature-pressure combinations. The higher theair temperature, the lower the pressure required to produce a yarnhaving a given value of residual shrinkage. Often, for the presentpurposes, it is preferred to employ high temperature fluids at reducedpressure, thereby decreasing the consumption of such fluids. in Examplesil -VI the yarn is packaged at a spindle-type Windup primarily toprovide low tension during packaging. The amount of twist imparted inall cases is low, since the yarns are interlaced and hence do notrequire twist.

Fluid jets most useful in the practice of this invention are those ofthe interlacing variety shown in detail in the above-mentioned patentapplication to Bunting and Nelson. Texturing jets, such as those shownin US. 2,852,906 to Breen are nearly as eifective, especially the jetshown in FIGURE of that patent. In certain applications the torque jetsshown in Belgian Patent 567,586 to Breen and Sussman, can be useful,since yarn bundle opening is believed to attend their operation,although such opening or filament separation does not occur to as greatan extent as in the above-described interlacing and texturing jets. Theproduct of the torque jet would b either relaxed zero-twist yarn or,provided the rate of twisting is suitably varied, a relaxed stablealternating twist yarn. In general, the apparatus which are useful asrelaxing means in this invention are those in which high-velocity fluidcan encounter a running yarn in a confined region or passageway,preferably in a near-perpendicular direction. Optimum relaxing andinterlacing is achieved when the yarn is acted upon by zone ofcontrolled fluid turbulence formed by a plurality of fiuid vortices, theaxes of which are substantially parallel to the axis of the runningyarns at the time of contact.

Winding tensions satisfactory for the process of this invention arebetween about 0.06 to about 0.35 g.p.d., with a preferred range of from0.1 to 0.25 g.p.d. In controlled relaxations greater than about 12%, thewindup tension preferably is less than about 0.15 g.p.d. for decreasedresidual shrinkage. Such tensions are conveniently obtained by use ofthe proper size traveler on the twister ring, considering also thedenier of the yarn being wound, as is well known to those skilled in theart. In this connection, it has been observed that a winding tension ofabout 2 rams absolute represents the least tension which can be used ina practical process for winding lowdenier yarns. Alternatively, suitabletension devices may be used for other types of traversing and windingmechanisms. It is essential to maintain winding tension high enough toprevent sloughing of the package during ship merit, but low enough toprevent objectionable retensio-ning of the yarn. In general, underotherwise the same processing conditions, lower levels of yarn tensionpermit a proportionately greater improvement in residual shrinkage andshrinkage uniformity, both being achieved with improved operability upto the upper limits of relaxation of this invention.

Since the product of this invention is an interlaced yarn, it need notbe packaged at twisting windup, since an interlaced yarn already has thehandling and take-ofi' characteristics of a twisted structure. inaddition, it is advantageous to use the process of this invention inwinding squareor tapered-shouldered packages upon cylindrical bobbinsusing conventional reciprocating traverses (in which no twist isinserted), thereby decreasing shrinkage differences between yarn on theinside and the outside of such packages. This improvement is obtained byapplying a suitable tension to the yarn prior to winding. This inventionmakes it possible to wind freshly drawn polyamide yarn on paper(cardboard) cores, thus providing a single-use o-r one-way shippingpackage in one operation. On the other hand at high relaxations it isoften preferred to use a ring-traveler windup because of the low anduniform tension at which the yarn is wound onto the package. Similarly,the use of the filling wind permits similar uniformity of yarn take-offtension.

The yarn counts for which this invention is useful may range frommonofilament yarns to any desired number of filaments; for heavy denieryarns, it may sometimes be necessary to increase the heating time ortemperature in the fluid jet to compensate for the greater mass of thefilament bundle. In particular, the upper limit of relaxation has beenobserved to depend on the denier of the yarn being relaxed and on theextent to which it has been drawn. After relaxing with extremely hot airit may be desirable in some cases to treat the yarn with moisture,preferably prior to packaging, in order to permit the yarn to regain itsnormal moisture content.

The process of this invention is especially useful for synthetic linearpolyamides; by synthetic linear polyamides is meant those disclosed, forexample, by Garethers in U.S. Patents 2,071,250 and 2,071,253. Thepreparation and spinning of such polyamides is disclosed in US. Patents2,130,948; 2,163,636; and 2,477,156. Examples of such polyamides arethose prepared from suitable diamines and suitable dicarboxylic acids,such as hexamethylene diamine and adipic acid. Similarly, polyamidesfrom omega aminocar'ooxylic acids or their amideforming derivatives,e.g., polyamide from caprolactam, are included. Additional suitablepolymeric compositions include polyesters, such as -poly(ethyleneterephthalate) and poly(trans-phexahydrcxylylene terephthalate) orcopoiymers thereof as in the copolymer of the terephthalate with theisophthalate; vinyl polymers, such as poly(vinyl chloride),poly(vinylidene chloride), or copolymers thereof; polyhydrocarbons, suchas polyethylene and polypropylene and any other relaxable polymer.

The process of this invention can be used to relax and interlace stapleor continuous filament yarns. The elements of the process may be variedto produce slub yarns, variable denier yarns, thick and thin yarns, andyarns with varying interlacing density. This process can also becombined with a setting step as taught in Belgian Patent 567,997 toPitzl.

The relaxed interlaced yarn of this invention is useful in allapplications which require a twisted yarn, i.e., those in which thehandling and running characteristics of nominal zero-twist yarn are notalways satisfactory. Such an interlaced yarn can be prepared rapidly andcontinuously, and is stable, the interlaced structure not being removedby application of normal tension. Use of the yarns prepared inaccordance with this invention results in woven and knit fabrics ofexcellent uniformity and freedom from barre. Yarns prepared viahigh-temperature steam are deeper dyeing as well as more uniform.Numerous other advantages inherent in the practice of this inventionwill be readily apparent to those undertaking its practice.

We claim:

1. An improved process for forming an nntwisted compact yarn having asufiiciently low residual shrinkage to be wound and stored on lightcardboard cores, which comprises forwarding a relaxable syntheticpolymeric multi-filament yarn structure at a uniform positive tensionthrough an substantially enclosed yarn interlacing and relaxin zone,directing a stream of heated fluid into said zone with suflicient forceand velocity to separate the elements of the structure for maximum heattransfer to said elements and interlace them into a unitary structurewhile simultaneously permitting said elements to relax in a controlledamount to form a stable compact strand with substantially zero bundletwist characteristics existing uniformly throughout its length, and thenwinding said structure into a package at a sutficiently low tension thatsubstantial elongation is avoided.

2. The improved process of claim 1 wherein the structure comprises asynthetic polymeric composition selected from the group consisting ofpolyamides and polyesters.

3. The improved process of claim 1 wherein the heated fluid is at atemperature of at least about 150 C.

eaese 4. The improved process of claim 1 wherein the amount ofrelaxation is in excess of about 7%, based on any unit length of afilament before forwarding to the interlacing and relaxing zone.

5. The improved process of claim 4 wherein the winding tension isbetween about 0.05 and about 0.35 gpd.

6. The improved process of claim 5 wherein the amount of relaxation isin excess of about 12% and the windin tension is between about 0.05 andabout 0.15.

7. The improved process of claim 5 wherein the amount of relaxation isbetween about 7% and about 12%.

8. An improved process for producing an untwisted compact yarn havin asutliciently low residual shrinkage to be wound and stored on lightcardboard cores and a low incidence of filament breakage duringprocessing treatments which comprises forwarding a relaxablemultifilament yarn structure of a polymeric composition selected fromthe group consisting of polyamides and polyesters, at a uniform positivetension, through a substantially enclosed yarn interlacing and relaxingzone, directing a stream of fiuid heated to a temperature of at leastabout 150 C. into said zone at suflicient pressure and velocity to causeturbulence sufficient to separate the filaments of the structure formaximum transfer of heat from the fluid to the filaments and interlacethem into a unitary sfructure, While simultaneously permitting thefilaments of the structure to relax in a controlled amount in excess ofabout 7%, based on the length of the filaments of the structure to forma stable compact strand with substantially zero bundle twistcharacteristics exist ing uniformly throughout its length, and thenwinding the yarn into a package at a tension between about 0.05 andabout 0.35.

9. The improved process of claim 8 wherein the fluid is at a pressurebetween about 10 and about p.s.i.g.

10. The improved process of claim 9 wherein the fluid is air, heaed to atemperature between about 200 C. and about 500 C.

11. The improved process of claim 10 wherein the air is at a pressurebetween about 15 and about 30 p.s.i.g.

12. The improved process of claim 11 wherein the amount of relaxation isin excess of 12%.

References Cited in the file of this patent UNITED ST TES PATENTS2,564,245 Billion Aug. 14, 1951 2,584,779 Averns et a1. Feb. 5, 1952'2,751,747 Eurleson June 26, 1956 2,807,863 Schenker Oct. 1, 19572,846,839 Billion Aug. 12, 1958 2,869,967 Breen Jan. 20, 1959 FOREIGNPATENTS 554,149 Canada Mar. 11, 1958 554,150 Canada Mar. 11, 19581,178,980 France Dec. 15, 1958 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 3,069,836 December 25, 1962 Richard LeeDahlstrom et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

In the sheet of drawings, FIG,3a, strike out the reference numeral "23";same FIG. 3a, for the reference numeral "24" read 24a FIG, 4, strike outthe reference numeral "25" column 3, line 24, after "'mll" infse 'tportion same line 241 for "19" read 29 line 26, after "over" insert ansame line 26, after "roll" strike out "20"; line 28, after n "roll"insert portion line 33, for "19" read 29 line 4?, for '"inventionoFluid" read invention. The fluid same line, strike out "2"; line 48,strike out "23"; line 50, after "on" insert the lengthwise yarn sameline, strike out "23"; line 53, strike out "23"; line 56, for"perpendicular. Fluid" read perpendicular. The fluid same line 56 strikeout "2"; 'line 57', for "28" read 25 line 58, before "fluid" insert thesame line 58, strike 'out "2" l1nes'63 and 71, strike out "'25", eachoccurrence.

Signed and sealed this 17th day of September 1963,.

SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

